Window lifters in motor vehicles serve to adjust the position of a window pane within a vehicle bodywork, within a swing door, within a tailgate or within a sliding door. In order, for example, to obtain a desired speed profile, a motor current of a drive of the window lifter is controlled by means of a power driver, for example a power semiconductor. Furthermore, it is desirable to sense the position of the window pane in order to control the adjustment movement and/or a collision protection means as a function of the sensed position.
An example of a window lifter having a drive is described in German laid-open patent application DE 43 02 143 A1. In this window lifter, the drive motor has a rotor which can be displaced axially. When the drive current for the drive motor is switched off, the rotor is moved into a locked position as a result of which the drive motor and thus the drive as a whole can be blocked.
DE 102 53 643 A1 is based on the basic idea of preventing a plurality of window lifters simultaneously closing completely the window pane assigned to them. Instead, only the window lifter which first closes the window pane is allowed to close the window pane to an extent at which the window lifter motor is blocked and the blocking current flows. All the other window lifter motors are switched off with timing such that the window pane does not reach its completely closed position, but rather only an approximately closed position. As soon as a window pane enters this end region, a blocking signal is emitted by a control unit of the corresponding window lifter and is transmitted via a bus system to all the other control units of the window lifters.
U.S. Pat. No. 6,253,135 B1 discloses a method for controlling a plurality of window lifters of a motor vehicle. DE 102 08 323 A1 relates to a motor-operated window system for a vehicle. The motor-operated window system comprises a window which can move between an open position and a closed position. The motor-operated window system also comprises a motor which is coupled to the window, the motor selectively causing the window to move. The motor-operated window system also comprises at least one switch and a communications bus which is coupled to the motor. The motor-operated window system also comprises a processor that is connected at least to the switch or the communications bus and is designed to selectively transmit at least one closing signal or opening signal to at least the switch or the communications bus. The motor-operated window system also comprises a sensor which is connected to the processor and which senses states on which automatic closing of the window is based.